Oil production and communication applications in subsea environments require electric devices able to withstand high pressure. However, electronic components, such as capacitors, particularly conventional electrolytic capacitors or MP capacitors are not applicable under high pressure conditions. Such capacitors exhibit electrodes stacked and rolled up in a casing partially filled with an electrolytic fluid, which would collapse under high pressure. Electric devices containing such electronic components are often designed with a pressure proof housing in order to keep the interior of the housing at atmospheric pressure (1 atm). Due to the high pressure in deep sea environments this housing needs to be adequately massive thus causing high costs. Further drawbacks are the high effort for sealing the housing and the feedthroughs for electrical connections to the outside. In other known approaches the housing of such electric devices is filled with an electrically insulating fluid. Although this allows a lightweight design of the device housing, the risk of damage to the capacitors persists because they are exposed to the ambient pressure transmitted by fluid in the device housing.
U.S. Pat. No. 5,876,872 discloses a battery with at least one electrochemical cell for use and recharging underwater, particularly seawater, at a pressure at or greater than atmospheric pressure. The battery has an anode, a cathode and an associated electrolyte in a housing. A pressure compensating fluid with a greater density than water separates the electrolyte from the surrounding water.
WO 00/76013 A1 discloses a battery for underwater use comprising a plurality of elements. Each element is provided with an aperture communicating with an external liquid environment. Each element is filled with liquid means for separating an electrolyte inside the element from the external liquid environment.